I have a 15" Titanium pbG4 with MATSHITA DVD-R UJ-815 superdrive, running 10.4.3. It has taken to not recognising any disks (DVD, blank or CD audio), going zzz-zzz, zzz-zzz and then spitting them out again. I assume this means the drive is dead. Can I replace it, or do I have to spend £££ getting a dealer to do it, and if so, is it even worth doing?